The custom firmware is only available for specific versions of the standard firmware, but from CF version 3.00 onwards the standard firmware is included with the CF download. The relevant downloads are available via the Wiki page HERE (click). Instructions for installing the downloads are on the forum HERE (click) or the Wiki HERE (click).
It could even be argued that, as the first to market, Humax, with its launch of the HD-Fox T2, isn't late at all. The set-top-box specialist is, relatively-speaking, ground-breakingly early. LnApH5w.